February 13, 2009
A ‘gross’ distortion
The spirited debate over the validity of the fabled hockey-stick graph on climate change continues.
The hockey-stick graph, an icon of global warming doomsayers that purported to show temperatures on Earth at record levels, in 2006 became the subject of investigations by two high-level scientific panels commissioned by the National Academy of Sciences and the U.S. House of Representatives. The former, chaired by Gerald North of Texas A&M, seemingly vindicated the controversial graph and its creator, scientist Michael Mann; the latter, chaired by Edward Wegman, ironically the National Academy of Sciences’s own Chair of its Committee on Applied and Theoretical Statistics, unequivocally determined the hockey stick to be based on shoddy science. North this week re-enters the debate in a letter to the Post, supporting the views of singer-songwriter Dave Clarke. They are both commenting on an exchange that appeared on this page last Saturday between Mann and Post columnist Lawrence Solomon. The hockey-stick debate continues below with comments by Clarke and North, followed by a response from Mr. Solomon.
Comment by Dave Clarke, Guitarist, Singer-Song-writer, Victoria
Solomon misrepresented Mann
I am writing you concerning the piece, “Manns conclusions not to be believed,” by Lawrence Solomon.
Regarding the conclusions of the National Academy of Sciences (NAS) panel concerning the Mann et al. study, Solomon writes:
“The NAS did find some of Mann’s work ‘plausible’ — that’s the closest that it comes to actually supporting Mann’s findings but then it immediately states there are so many scientific uncertainties attached to Mann’s work that it doesn’t have great confidence in it. The committee then proceeds to further downgrade its view of Mann’s work: “Even less confidence can be placed in the original conclusions by Mann et al. (1999) that ‘the 1990s are likely the warmest decade, and 1998 the warmest year, in at least a millennium.’ ” This is a gross misrepresentation of the NAS panel’s findings. The executive summary states: “Based on the analyses presented in the original papers by Mann et al. and this newer supporting evidence, the committee finds it plausible that the Northern Hemisphere was warmer during the last few decades of the 20th century than during any comparable period over the preceding millennium.”
Clearly, if the committee found it “plausible” that the last “last few decades of the 20th century [were warmer] than during any comparable period over the preceding millennium,” then Mann’s conclusion that “the ’90s are likely the warmest decade” of the past millennium is also plausible, albeit with less statistical confidence than in the post-1600 case, or when analyzing multi-decade periods.
Solomon is also wrong when he says, that this is the “closest” the committee comes to “actually supporting Manns findings.”
Consider this statement:
“The basic conclusion of Mann et al. (1998, 1999) was that the late 20th-century warmth in the Northern Hemisphere was unprecedented during at least the last 1,000 years. This conclusion has subsequently been supported by an array of evidence that includes both additional large-scale surface temperature reconstructions and pronounced changes in a variety of local proxy indicators, such as melting on ice caps and the retreat of glaciers around the world, which in many cases appear to be unprecedented during at least the last 2,000 years.”
The report also refers to the “high level of confidence we place in the Little Ice Age cooling and 20th century warming.”
Moreover, proceedings of the National Academy of Science recently published the latest Mann et. al paleoclimate study, which builds on the previous pioneering work. This is obviously at odds with Solomon’s characterization of at best lukewarm NAS support for Mann’s research and conclusions.
Of course, I object to many other aspects of Solomon’s disgraceful piece, particularly his characterization of Mann’s work as a “statistical sham.” And I do not mean to suggest that the above are the only errors or misrepresentations to be found in Solomon’s diatribe.
But I do urge you to correct the errors concerning the NAS report as soon as possible. In this connection, you may wish to correspond with the chairman of the NAS panel, Gerald North. For the convenience of all the parties I have copied Dr. North on this correspondence.
Comment by Gerald R. North, former chair, National Academy of Sciences
North concurs with Clarke
I have to agree with Mr. Clarke. Your article about the NAS reports is quite misleading — in fact, a shameful misrepresentation.
But I do not wish to engage in further discussion in your paper/blog.
Under oath, North faults Mann too
by Lawrence Solomon, National Post, February 16, 2009
Gerald North’s panel ruled that Michael Mann’s conclusion was right even if his study provided no basis for that conclusion, despite the response above.
Of all the scientists who have come to Michael Mann’s defence, none have more impressive credentials than those of Gerald North, a former Head of the Department of Atmospheric Sciences at Texas A&M University. North, a physicist, has not only spent decades addressing the dangers of climate change, he has done so through his work in climate models and his knowledge of statistics, a suite of qualifications that make him particularly well qualified to comment on Michael Mann’s statistics-based work. Because of his background, and because Mann’s hockey-stick graph had become a source of great controversy, the National Academy of Sciences (NAS) asked North to chair a panel to investigate the statistical validity of the hockey stick graph. The NAS, like most national academies, backs the man-made global warming thesis.
The North report for the NAS, published in June, 2006, was released at a press conference and with a press release entitled: “High Confidence’ That Planet Is Warmest in 400 Years; Less Confidence in Temperature Reconstructions Prior to 1600.” Because the press release, the report, and North himself made many statements favourable to Mann, the worldwide press understandably reported that Mann had been vindicated.
“Science Panel Backs Study on Warming Climate,” read the New York Times headline. “Academy affirms hockey-stick graph” read that of Nature magazine. “Global warming is real, according to America’s top scientists, who say the earth is running its highest fever in hundreds of years,” stated NBC Nightly News anchor Brian Williams.
But the story that North and other panel members relayed less than one month later, when they were required to testify under oath, showed the NAS report to be the opposite of what most had assumed. The setting was now not a press conference but formal hearings before the Energy and Commerce Committee of the U.S. House of Representatives. Because Mann had refused to provide other researchers with the computer code necessary to verify his work, because the credibility of the science surrounding the hockey stick had become a cause célèbre, and because federal government funds had financed the hockey stick study, the Energy and Commerce committee the previous summer had decided to hold hearings into the matter.
The committee then commissioned a study by Edward Wegman, arguably America’s top statistician, and arranged for him to testify in July, 2006. Meanwhile, the NAS decided to produce a competing study into the Mann controversy, with North as its chair. The Energy and Commerce committee then decided to have Wegman and North both testify before it.
Wegman’s testimony powerfully demonstrated that Mann’s work had no validity. Then North testified in Mann’s defence, also powerfully, by showing that Mann’s conclusions were valid.
Who was right and what was going on? The following exchange between the committee chairman, Joe Barton, and North establishes who was right.
CHAIRMAN BARTON Dr. North, do you dispute the conclusions or the methodology of Dr. Wegman’s report?
DR. NORTH No, we don’t. We don’t disagree with their criticism. In fact, pretty much the same thing is said in our report.
Barton then asked North’s colleague on the NAS panel, Peter Bloomfield, a similar question. Bloomfield’s reply: “Our committee reviewed the methodology used by Dr. Mann and his co-workers and we felt that some of the choices they made were inappropriate. We had much the same misgivings about his work that was documented at much greater length by Dr. Wegman.”
What was going on? North’s NAS panel confirmed, without stating so clearly, that Mann’s science was shoddy, and that Mann’s conclusions, on their own, could not be trusted. But that didn’t mean that Mann’s answer was wrong — North’s panel believed that man-made global warming exists and they had lots of evidence, by other scientists, to support their belief. Therefore, the NAS panel concluded, Mann was right in his ultimate conclusion that man causes global warming, even if Mann’s study provided no basis for that conclusion.
The press can be forgiven for believing that the National Academy of Sciences panel chaired by North had vindicated the science behind the hockey stick graph, and so can singer-songwriter David Clarke.
Lawrence Solomon is executive director of Energy Probe and author of The Deniers: The world-renowned scientists who stood up against global warming hysteria, political persecution, and fraud.
Edward J. Wegman, C.V.